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    <title>BOOST_PP_FOR_r</title>
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    <div style="margin-left:  0px;"> The <b>BOOST_PP_FOR_<i>r</i></b> macro
      represents a reentry into the <b>BOOST_PP_FOR</b> repetition construct. </div>
    <h4>Usage</h4>
    <div class="code"> <b>BOOST_PP_FOR_</b> ## <i>r</i>(<i>state</i>, <i>pred</i>,
      <i>op</i>, <i>macro</i>) </div>
    <h4>Arguments</h4>
    <dl>
      <dt>r</dt>
      <dd> The next available <b>BOOST_PP_FOR</b> repetition. </dd>
      <dt>state</dt>
      <dd> The initial state. </dd>
      <dt>pred</dt>
      <dd> A binary predicate of the form <i>pred</i>(<i>r</i>, <i>state</i>).&nbsp;
        This macro must expand to an integer in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.&nbsp;
        <b>BOOST_PP_FOR</b> repeatedly expands <i>macro</i> while this
        predicate returns non-zero.&nbsp; This macro is called with the next
        available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>.
      </dd>
      <dt>op</dt>
      <dd> A binary operation of the form <i>op</i>(<i>r</i>, <i>state</i>).&nbsp;
        This operation is expanded by <b>BOOST_PP_FOR</b> with the next
        available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>.&nbsp;
        This macro is repeatedly applied to the <i>state</i>, each time
        producing a new <i>state</i>, until <i>pred</i> returns <i>0</i>. </dd>
      <dt>macro</dt>
      <dd> A binary macro of the form <i>macro</i>(<i>r</i>, <i>state</i>).&nbsp;
        This macro is expanded by <b>BOOST_PP_FOR</b> with the next available <b>BOOST_PP_FOR</b>
        repetition and the current <i>state</i>.&nbsp; This macro is is
        repeated by <b>BOOST_PP_FOR</b> until <i>pred</i> returns <i>0</i>. </dd>
    </dl>
    <h4>Remarks</h4>
    <div> This macro expands to the sequence:
      <div> <i>macro</i>(<i>r</i>, <i>state</i>) <i>macro</i>(<i>r</i>, <i>op</i>(<i>r</i>,
        <i>state</i>)) ... <i>macro</i>(<i>r</i>, <i>op</i>(<i>r</i>, ... <i>op</i>(<i>r</i>,
        <i>state</i>) ... )) </div>
    </div>
    <div> At certain times, it may be necessary to perform the concatenation
      with <b>BOOST_PP_CAT</b> rather than the preprocessor token-pasting
      operator.&nbsp; This happens when the <i>r</i> value is a macro
      invocation itself.&nbsp; It needs a delay to allow it to expand.&nbsp; The
      syntax in such a scenario becomes:
      <div> <b>BOOST_PP_CAT</b>(<b>BOOST_PP_FOR_</b>, <i>r</i>)(<i>state</i>,
        <i>pred</i>, <i>op</i>, <i>macro</i>) </div>
    </div>
    <h4>See Also</h4>
    <ul>
      <li><a href="cat.html">BOOST_PP_CAT</a></li>
      <li><a href="for.html">BOOST_PP_FOR</a></li>
      <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
      <li><a href="for_r_macros.html"><span style="color: gray;">Macros with R
            re-entrancy forms</span></a></li>
    </ul>
    <h4>Requirements</h4>
    <div> <b>Header:</b> &nbsp;<a href="../headers/repetition/for.html">&lt;boost/preprocessor/repetition/for.hpp&gt;</a>
    </div>
    <h4>Sample Code</h4>
    <div>
      <pre>#include &lt;<a href="../headers/arithmetic/dec.html">boost/preprocessor/arithmetic/dec.hpp</a>&gt;
#include &lt;<a href="../headers/arithmetic/inc.html">boost/preprocessor/arithmetic/inc.hpp</a>&gt;
#include &lt;<a href="../headers/comparison/not_equal.html">boost/preprocessor/comparison/not_equal.hpp</a>&gt;
#include &lt;<a href="../headers/punctuation/comma_if.html">boost/preprocessor/punctuation/comma_if.hpp</a>&gt;
#include &lt;<a href="../headers/repetition/for.html">boost/preprocessor/repetition/for.hpp</a>&gt;
#include &lt;<a href="../headers/tuple/elem.html">boost/preprocessor/tuple/elem.hpp</a>&gt;

#define PRED(r, state) \
   <a href="not_equal.html">BOOST_PP_NOT_EQUAL</a>( \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), \
      <a href="inc.html">BOOST_PP_INC</a>( \
         <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state) \
      ) \
   ) \
   /**/

#define OP(r, state) \
   ( \
      <a href="inc.html">BOOST_PP_INC</a>( \
         <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \
      ), \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state), \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 2, state), \
      <a href="inc.html">BOOST_PP_INC</a>( \
         <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 3, state) \
      ) \
   ) \
   /**/

#define MACRO(r, state) \
   <a href="comma_if.html">BOOST_PP_COMMA_IF</a>( \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 3, state) \
   ) template&lt; \
      <a href="for_r.html">BOOST_PP_FOR_</a> ## r( \
         (0, <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), _, 0), \
         PRED_2, OP, MACRO_2 \
      ) \
   &gt; class <a href="cat.html">BOOST_PP_CAT</a>( \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 2, state), \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \
   ) \
   /**/

#define PRED_2(r, state) \
   <a href="not_equal.html">BOOST_PP_NOT_EQUAL</a>( \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state) \
   ) \
   /**/

#define MACRO_2(r, state) \
   <a href="comma_if.html">BOOST_PP_COMMA_IF</a>( \
      <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \
   ) class \
   /**/

#define TEMPLATE_TEMPLATE(low, high, name) \
   <a href="for.html">BOOST_PP_FOR</a>( \
      (low, high, name, 0), \
      PRED, OP, MACRO \
   ) \
   /**/

TEMPLATE_TEMPLATE(2, 4, T)
/*
   expands to...
   template&lt;class, class&gt; class T2,
   template&lt;class, class, class&gt; class T3,
   template&lt;class, class, class, class&gt; class T4
*/
</pre></div>
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    <div style="margin-left: 0px;"> <i>© Copyright <a href="http://www.housemarque.com"
          target="_top">Housemarque Oy</a> 2002</i> <br>
      <i>© Copyright Paul Mensonides 2002<br>
      </i><i>© Copyright Edward Diener 2014</i><br>
    </div>
    <div style="margin-left: 0px;">
      <p><small>Distributed under the Boost Software License, Version 1.0. (See
          accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
          or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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